1. Field
The present application discloses an apparatus for bonding substrates, and more particularly, a substrate bonding apparatus having an alignment unit enabling six-degrees-of-freedom alignment using a plurality of actuators. A method of aligning substrates using such an apparatus is also disclosed.
2. Background
A substrate bonding apparatus is used to bond two substrates of a flat panel display device to each other. Examples of such display devices include TFT-LCD panels, PDPs, OLEDs and the like. In the case of a TFT-LCD panel, a TFT substrate is bonded with a color filter substrate. Typically, the gap between the substrates is only a few micrometers. The TFT substrate is provided with multiple TFTs (thin film transistors) formed in a matrix form and the color filter substrate is formed with a color filter, a light shield film and the like.
The substrate bonding is carried out by pressing the two substrates together. For this purpose, the substrate bonding apparatus includes a first chamber and a second chamber which are positioned opposite each other. Each chamber is provided with a surface plate, on which a substrate can be held. One chamber then moves towards the other chamber while the substrates are maintained parallel to each other, and aligned in an X-axis and Y-axis directions. As the substrates are brought together, bonding of the two substrates is performed.
If the two surface plates are not properly aligned and held parallel to one another, an alignment error may occur during the substrate bonding process. Therefore, while the bonding process is being conducted, accurate alignment of the surface plates must be ensured.
In background art devices, surface plates are mounted in the first and second chambers, and the substrates are held on the surface plates. The relative positions of the two surface plates are adjustable, typically using one or more bolts. The surface plates are usually aligned manually using a leveler and a level-adjustment tool.